diff --git a/src/p_3dfloors.h b/src/p_3dfloors.h
index 5ddded3d3..51761d31b 100644
--- a/src/p_3dfloors.h
+++ b/src/p_3dfloors.h
@@ -90,7 +90,7 @@ struct F3DFloor
 	
 	fixed_t				delta;
 	
-	int					flags;
+	unsigned int		flags;
 	line_t*				master;
 	
 	sector_t *			model;
diff --git a/src/p_3dmidtex.cpp b/src/p_3dmidtex.cpp
index 3338956f3..5d5ba56d8 100644
--- a/src/p_3dmidtex.cpp
+++ b/src/p_3dmidtex.cpp
@@ -228,7 +228,7 @@ bool P_GetMidTexturePosition(const line_t *line, int sideno, fixed_t *ptextop, f
 	FTexture * tex= TexMan(texnum);
 	if (!tex) return false;
 
-	fixed_t totalscale = FixedMul(side->GetTextureYScale(side_t::mid), tex->yScale);
+	fixed_t totalscale = abs(FixedMul(side->GetTextureYScale(side_t::mid), tex->yScale));
 	fixed_t y_offset = side->GetTextureYOffset(side_t::mid);
 	fixed_t textureheight = tex->GetScaledHeight(totalscale) << FRACBITS;
 	if (totalscale != FRACUNIT && !tex->bWorldPanning)
diff --git a/src/p_sight.cpp b/src/p_sight.cpp
index 259b3baa8..b007410c8 100644
--- a/src/p_sight.cpp
+++ b/src/p_sight.cpp
@@ -56,7 +56,7 @@ class SightCheck
 	fixed_t topslope, bottomslope;	// slopes to top and bottom of target
 	int Flags;
 	divline_t trace;
-	int myseethrough;
+	unsigned int myseethrough;
 
 	bool PTR_SightTraverse (intercept_t *in);
 	bool P_SightCheckLine (line_t *ld);
diff --git a/src/r_segs.cpp b/src/r_segs.cpp
index 30738e657..b738b1c10 100644
--- a/src/r_segs.cpp
+++ b/src/r_segs.cpp
@@ -171,31 +171,30 @@ fixed_t MaskedScaleY;
 
 static void BlastMaskedColumn (void (*blastfunc)(const BYTE *pixels, const FTexture::Span *spans), FTexture *tex)
 {
-	if (maskedtexturecol[dc_x] != FIXED_MAX)
+	// calculate lighting
+	if (fixedcolormap == NULL && fixedlightlev < 0)
 	{
-		// calculate lighting
-		if (fixedcolormap == NULL && fixedlightlev < 0)
-		{
-			dc_colormap = basecolormap->Maps + (GETPALOOKUP (rw_light, wallshade) << COLORMAPSHIFT);
-		}
-
-		dc_iscale = MulScale18 (MaskedSWall[dc_x], MaskedScaleY);
-		sprtopscreen = centeryfrac - FixedMul (dc_texturemid, spryscale);
-		
-		// killough 1/25/98: here's where Medusa came in, because
-		// it implicitly assumed that the column was all one patch.
-		// Originally, Doom did not construct complete columns for
-		// multipatched textures, so there were no header or trailer
-		// bytes in the column referred to below, which explains
-		// the Medusa effect. The fix is to construct true columns
-		// when forming multipatched textures (see r_data.c).
-
-		// draw the texture
-		const FTexture::Span *spans;
-		const BYTE *pixels = tex->GetColumn (maskedtexturecol[dc_x] >> FRACBITS, &spans);
-		blastfunc (pixels, spans);
-//		maskedtexturecol[dc_x] = FIXED_MAX; // kg3D - seems to be useless
+		dc_colormap = basecolormap->Maps + (GETPALOOKUP (rw_light, wallshade) << COLORMAPSHIFT);
 	}
+
+	dc_iscale = MulScale18 (MaskedSWall[dc_x], MaskedScaleY);
+ 	if (sprflipvert)
+		sprtopscreen = centeryfrac + FixedMul(dc_texturemid, spryscale);
+	else
+		sprtopscreen = centeryfrac - FixedMul(dc_texturemid, spryscale);
+	
+	// killough 1/25/98: here's where Medusa came in, because
+	// it implicitly assumed that the column was all one patch.
+	// Originally, Doom did not construct complete columns for
+	// multipatched textures, so there were no header or trailer
+	// bytes in the column referred to below, which explains
+	// the Medusa effect. The fix is to construct true columns
+	// when forming multipatched textures (see r_data.c).
+
+	// draw the texture
+	const FTexture::Span *spans;
+	const BYTE *pixels = tex->GetColumn (maskedtexturecol[dc_x] >> FRACBITS, &spans);
+	blastfunc (pixels, spans);
 	rw_light += rw_lightstep;
 	spryscale += rw_scalestep;
 }
@@ -226,7 +225,7 @@ void R_RenderMaskedSegRange (drawseg_t *ds, int x1, int x2)
 	FTexture	*tex;
 	int			i;
 	sector_t	tempsec;		// killough 4/13/98
-	fixed_t		texheight, textop, texheightscale;
+	fixed_t		texheight, texheightscale;
 	bool		notrelevant = false;
 
 	const sector_t *sec;
@@ -308,9 +307,14 @@ void R_RenderMaskedSegRange (drawseg_t *ds, int x1, int x2)
 	spryscale = ds->iscale + ds->iscalestep * (x1 - ds->x1);
 	rw_scalestep = ds->iscalestep;
 
+	if (fixedlightlev >= 0)
+		dc_colormap = basecolormap->Maps + fixedlightlev;
+	else if (fixedcolormap != NULL)
+		dc_colormap = fixedcolormap;
+
 	// find positioning
 	texheight = tex->GetScaledHeight() << FRACBITS;
-	texheightscale = curline->sidedef->GetTextureYScale(side_t::mid);
+	texheightscale = abs(curline->sidedef->GetTextureYScale(side_t::mid));
 	if (texheightscale != FRACUNIT)
 	{
 		texheight = FixedDiv(texheight, texheightscale);
@@ -324,8 +328,18 @@ void R_RenderMaskedSegRange (drawseg_t *ds, int x1, int x2)
 		dc_texturemid = MIN (frontsector->GetPlaneTexZ(sector_t::ceiling), backsector->GetPlaneTexZ(sector_t::ceiling));
 	}
 
-	{ // encapsulate the lifetime of rowoffset
-		fixed_t rowoffset = curline->sidedef->GetTextureYOffset(side_t::mid);
+	fixed_t rowoffset = curline->sidedef->GetTextureYOffset(side_t::mid);
+
+	if (!(curline->linedef->flags & ML_WRAP_MIDTEX) &&
+		!(curline->sidedef->Flags & WALLF_WRAP_MIDTEX))
+	{ // Texture does not wrap vertically.
+		fixed_t textop;
+
+		if (MaskedScaleY < 0)
+		{
+			MaskedScaleY = -MaskedScaleY;
+			sprflipvert = true;
+		}
 		if (tex->bWorldPanning)
 		{
 			// rowoffset is added before the MulScale3 so that the masked texture will
@@ -341,16 +355,11 @@ void R_RenderMaskedSegRange (drawseg_t *ds, int x1, int x2)
 			textop = dc_texturemid - viewz + SafeDivScale16 (rowoffset, MaskedScaleY);
 			dc_texturemid = MulScale16 (dc_texturemid - viewz, MaskedScaleY) + rowoffset;
 		}
-	}
-
-	if (fixedlightlev >= 0)
-		dc_colormap = basecolormap->Maps + fixedlightlev;
-	else if (fixedcolormap != NULL)
-		dc_colormap = fixedcolormap;
-
-	if (!(curline->linedef->flags & ML_WRAP_MIDTEX) &&
-		!(curline->sidedef->Flags & WALLF_WRAP_MIDTEX))
-	{ // Texture does not wrap vertically.
+		if (sprflipvert)
+		{
+			MaskedScaleY = -MaskedScaleY;
+			dc_texturemid -= tex->GetHeight() << FRACBITS;
+		}
 
 		// [RH] Don't bother drawing segs that are completely offscreen
 		if (MulScale12 (globaldclip, ds->sz1) < -textop &&
@@ -467,6 +476,20 @@ void R_RenderMaskedSegRange (drawseg_t *ds, int x1, int x2)
 	}
 	else
 	{ // Texture does wrap vertically.
+		if (tex->bWorldPanning)
+		{
+			// rowoffset is added before the MulScale3 so that the masked texture will
+			// still be positioned in world units rather than texels.
+			dc_texturemid += rowoffset - viewz;
+			dc_texturemid = MulScale16 (dc_texturemid, MaskedScaleY);
+		}
+		else
+		{
+			// rowoffset is added outside the multiply so that it positions the texture
+			// by texels instead of world units.
+			dc_texturemid = MulScale16 (dc_texturemid - viewz, MaskedScaleY) + rowoffset;
+		}
+
 		WallC.sz1 = ds->sz1;
 		WallC.sz2 = ds->sz2;
 		WallC.sx1 = ds->sx1;
@@ -576,7 +599,7 @@ void R_RenderFakeWall(drawseg_t *ds, int x1, int x2, F3DFloor *rover)
 	}
 	xscale = FixedMul(rw_pic->xScale, scaledside->GetTextureXScale(scaledpart));
 	yscale = FixedMul(rw_pic->yScale, scaledside->GetTextureYScale(scaledpart));
-	// encapsulate the lifetime of rowoffset
+
 	fixed_t rowoffset = curline->sidedef->GetTextureYOffset(side_t::mid) + rover->master->sidedef[0]->GetTextureYOffset(side_t::mid);
 	dc_texturemid = rover->model->GetPlaneTexZ(sector_t::ceiling);
 	rw_offset = curline->sidedef->GetTextureXOffset(side_t::mid) + rover->master->sidedef[0]->GetTextureXOffset(side_t::mid);
@@ -2508,9 +2531,9 @@ void R_StoreWallRange (int start, int stop)
 				iend = DivScale32 (1, iend);
 				ds_p->yrepeat = yrepeat;
 				ds_p->iscale = istart;
-				if (stop - start > 1)
+				if (stop - start > 0)
 				{
-					ds_p->iscalestep = (iend - istart) / (stop - start - 1);
+					ds_p->iscalestep = (iend - istart) / (stop - start);
 				}
 				else
 				{
diff --git a/src/textures/pngtexture.cpp b/src/textures/pngtexture.cpp
index 5a3ae960a..6a7370fac 100644
--- a/src/textures/pngtexture.cpp
+++ b/src/textures/pngtexture.cpp
@@ -276,9 +276,9 @@ FPNGTexture::FPNGTexture (FileReader &lump, int lumpnum, const FString &filename
 			lump.Read (trans, len);
 			HaveTrans = true;
 			// Save for colortype 2
-			NonPaletteTrans[0] = BigShort(((WORD *)trans)[0]);
-			NonPaletteTrans[1] = BigShort(((WORD *)trans)[1]);
-			NonPaletteTrans[2] = BigShort(((WORD *)trans)[2]);
+			NonPaletteTrans[0] = WORD(trans[0] * 256 + trans[1]);
+			NonPaletteTrans[1] = WORD(trans[2] * 256 + trans[3]);
+			NonPaletteTrans[2] = WORD(trans[4] * 256 + trans[5]);
 			break;
 
 		case MAKE_ID('a','l','P','h'):